Characters may be the heart of any game, but any narrative or depth would be pointless were it floating in a void of nothing- the environment where the events take place is just as important as the events themselves, and this is more true for video games than any other media or art form. Your vision isn’t directed- you are free to explore everything the area has to offer.
However, free as you are, the environment needs to have some kind of route through it. If you are in a hub between levels this isn’t so important, but if you are supposed to get to the next area through a door that blends right in with the rest of the scenery, you hit a dead end, unsure of where to go next. The creators need to place indicators of where you are supposed to go- sometimes the designers do this, by placing a line of collectibles, ammo, health, etc leading to the door. But usually, it’s the art teams job to make that door, or the path to that door, stand out somehow, be it using colour to make the area around the door catch the eye straight away, or by placing obstacles that lead the player in a route around the room in a way that leads them to a position from which they can’t really miss the door.
The cult classic game Sphinx and the Cursed Mummy has many perfect examples; the game is absolutely full of some of the most beautiful and immersive environments- chances are, by the time you finish the game, you still haven’t seen all Abydos has to offer, and frustrating as the fetch-quest near the beginning can be, the chance to explore the secret passages and the dungeons of the royal palace alone was motivation enough. But the absolute perfect example here has to be Heliopolis, both from a visual and a design point of view. When you first arrive at Heliopolis, you see a temple, lots of sand, and some small huts and a huge wall off in the distance. The latter two are unreachable, however, guarded by the laser-shooting Eye of Ra statues. So naturally, your first stop is the temple, in which you find nothing useful- but upon exiting the temple, you find yourself facing a huge cave you may never have noticed otherwise, leading you to the dungeon. Later, when you can destroy the Eye of Ra statues and progress to the other side of the wall, you find a huge expanse of desert containing the next dungeon, a small village, and many places and items significant in the games various sidequests. The way the game leads you to where you need to go is simple, yet clever.
The Krazoa Palace in Starfox Adventures worked similarly. Each time you enter, you are dropped off at a different location, and are heading somewhere in the palace you haven’t been to before. To make things worse, the room you must pass through with each visit, your centre of navigation, is a maze of fans and air currents, meaning it would be easy to get lost. This time, you are directed by design rather than visually; each door is activated differently. You can’t go the wrong way because you either don’t have the item or ability needed to open the wrong routes yet, and the places you have already been are easily recognisable because it’s easy to spot how a door is supposed to be opened or how the route is to be navigated (a pair of dinosaur footprints in front of a locked door mean it’s opened by standing on it wearing the SharpClaw Disguise, while a door with a symbol on the wall nearby means it’s opened by shooting the symbol). Each floor of the central room is also distinguishable by the enemies, placed on each floor in varying number and type.